Human infertility is a global problem and failure of embryo implantation accounts for a significant percentage of pregnancy failure during both natural pregnancy and in vitro fertilization procedures. Implantation is an extremely complicated process requiring precisely controlled hormonal, growth factor signaling and cell-cell contacts which coordinate interactions between the competent blastocysts and the receptive uterus. Decidualization is part of the implantation process and involves rapid proliferation then differentiation of fibroblast-like endometrial stromal cells into epitheloid-like decidual cells whch later become part of the decidual tissue that surrounds the implanting conceptus. Decidualization defects can directly lead to implantation failure. In addition, early decidualizatin defects can also lead to other pregnancy defects such as placentation, intrauterine fetal growth, and parturition. Up to now, the process of decidualization has not been systematically studied due to the lack of a suitable high throughput screening tool. In this proposal, we propose to generate such much-needed tool using the recently developed state-of-the-art CRISPR/Cas genome editing technology. In Aim I we will use CRISPR to generate a dual-reporter cell line for decidualization by knocking two fluorescent reporters into endogenous loci of decidual markers. In Aim II, we will use this new tool to perform a small scale high throughput screening for chemical compounds that can interfere with decidualization. Successful completion of this project will have a long-lasting impact in multiple research fields including implantation biology, contraception, in vitro fertilization and environmental toxicology. .